Advances in research on human cerebral organoids (HCOs) call for a critical review of current research policies. A challenge for the evaluation of necessary research regulations lies in the severe uncertainty about future trajectories the currently very rudimentary stages of neural cell cultures might take as the technology progresses. To gain insights into organotypic cultures, ethicists, legal scholars, and neuroscientists rely on resemblances to the human brain. They refer to similarities in structural or functional terms that have been established in (...) scientific practice to validate organotypic cultures as models for brain research. In ethical discourse, however, such similarities are also used to justify assumptions about the potential risk to cause harm to HCOs. Ethicists assume that as the technology advances, organotypic cultures will increasingly resemble the human brain, raising more complex ethical issues. I argue that such reasoning is not justified given the heterogeneity of HCOs that have been modified to enable scientists to pursue their research goals. I then discuss the implications this line of thought has for advocates of the precautionary principle, focussing on those suggestions which propose adopting research regulations to the presence of bodily warning signs deemed worthy of protection. In doing so, I illustrate that the prevalent assumptions on similarity in ethical discourse ultimately risk disproportionately restricting research. I conclude that given the severe uncertainty about the technology’s future development, ethical discourse might benefit from narrowing the time frame for anticipation. (shrink)